This invention relates generally to optical temperature sensing techniques, and more specifically to such techniques applied to measure the internal temperature of objects being heated by electromagnetic radiation and/or ultrasonic energy.
There are many applications where the internal temperature of a fluid bath or more solid object is to be measured in an electromagnetic radiation and/or ultrasonic energy field that is heating the object. One such application is in the emerging field of medical hyperthermia, where tumors and cancerous tissue within a human body are heated by an external source as part of a program of medical treatment. For such treatment, the tumor is maintained at a pre-determined elevated temperature for a pre-determined period of time by directing electromagnetic radiation, in either the radio frequency or microwave spectrums, and/or ultrasonic energy from outside the body into the tumor.
In order to assure that the material being heated in this way is maintained at the desired temperature, a non-obtrusive temperature sensor is implanted in the material. In the case of cancer treatment of the human patient, such a sensor is surgically implanted in the region to be heated prior to beginning the heating. Very small thermocouples and thermistors are traditionally used with either ultrasonic energy or electromagnetic radiation heating. More recently, optical fiber temperature sensors are being employed to measure the temperature of materials heated by electromagnetic radiation. A significant advantage of the newer optical sensors is that they do not include electrically conducting materials, thereby eliminating heating of the sensor that can result from the use of thermocouples and thermistors as the result of electrical currents induced by the electromagnetic energy field. A significant source of error is thus eliminated. Since this problem of induced current does not exist with ultrasonic heating, however, thermocouples and thermistors remain the technique of choice for that type of heating.
It is a primary object of the present invention to provide an optical temperature sensing probe that may be used with a variety of specific types of heating without introducing excessive errors.